Method and apparatus for arc working with gas shields having coherentstreaming



Sept. 11, 1962 E. F. GORMAN ETAL 3,053,958

METHOD AND APPARATUS FOR ARC WORKING WITH GAS SHIELDS HAVINGCOHERENT-STREAMING 9 Sheets-Sheet 1 Filed April 25, 1960 INVENTORSEUGENE F. GORMAN ROBERT J. NELSON "WW4 ATTORNEY Sept. 11, 1962 FiledApril 25, 1960 E. F. GORMAN ETAL 3,053,968 METHOD AND APPARATUS FOR ARCWORKING WITH GAS SHIELDS HAVING COHERENT-STREAMING 9 Sheets-Sheet 2MODIFIED PERMEABLE BARRIER MODIFIED I6 GAS PORTS STANDARD 4 GAS PORTS xo x I l I I I 9 IO 20 30 4o 50 6O ARGON FLOW RATE C.F. H.

JNVENTORS EUGENE F. GORMAN ROBERT J. NELSON ATTORNEY Sept. 11, 1962 E.F. GORMAN ETAL METHOD AND APPARATUS FOR ARC WORKING WITH GAS I SHIELDSHAVING COHERENT-STREAIIIING Filed April 25, 1960 9 Sheets-Sheet 5NOZZLE-TOWORK ELEVATION- 5/8 INCH STANDARD .4 GAS PORTS MODIFIED 16 GASPORTS MODIFIED PERMEABLE BARRIER MODIFIED 16 GAS PORTS MODIFIEDPERMEABLE BARRIER INVENTORS EUGENE EGORMAN ROBERT J, NELSON A T TORNEISept. 11, 1962 E. F. GORMAN ETAL 3,053,968

METHOD AND APPARATUS FOR ARC WORKING WITH GAS SHIELDS HAVINGCOHERENT-STREAMING Filed April 25, 1960 9 Sheets-Sheet 4 MODIFIEDPERMEABLE BARRIER o I l NOZZLE-TO-WORK ELEVATIONJNCHES WELD SHIELDINGSPAN, INCHES 6*? g INVENTORS EUGENE F. GORMAN ROBERT J.NELSON Sept. 11,1962 E. F. GORMAN ETAL 3,053,968

METHOD AND APPARATUS FOR ARC WORKING WITH GAS SHIELDS HAVINGCOHERENT-STREAMING Filed April 25, 1960 9 Sheets-Sheet 5 INVENTORSEUGENE F. GORMAN ROBERT J. NELSON ByMx ATTORNEY pt 1962 E. F. GORMANETAL 3,053,968

METHOD AND APPARATUS FOR ARC WORKING WITH GAS SHIELDS HAVINGCOHERENT-STREAMING 9 Sheets-Sheet 6 Filed April 25, 1960 INVENTORSEUGENE F. GORMAN ROBERT J. NELSON BYWW ATTORNEY 9 Sheets-Sheet 7JNVENTORS EUGENE F. GORMAN ROBERT J. NELSON ATTORNEY2 E. F. GORMAN ETALATUS FOR ARC WORKING WITH GAS Sept. 11, 1962 METHOD AND APPAR SHIELDSHAVING COHERENT-STREAMING Filed April 25, 1960 Sept. 11, 1962 E. F.GORMAN ETAL 3,053,968

METHOD AND APPARATUS FoR ARC WORKING WITH GAS SHIELDS HAVINGCOHERENT-STREAMING Filed April 25, 1960 9 Sheets-Sheet 8 NOZ ZLE-TOWORK'E LEVATIO N -3/8 INCH STANDARD-'WWH NO. 10 NOZZLE NOZZLE-TO-WORKELEVATlON-3/B INCH MODIFIED-WITH FLAT GAS LENS AND NOJO NOZZLEVERTEX-TO-WORK ELEVATlON-1/2 INCH MODIFiED-WITH PARABOLIC GAS LENSINVENTORS EUGENE F. GORMAN ROBERT J. NELSON ATTORNEY p 1962 E. F. GORMANETAL 3,053,968

METHOD AND APPARATUS FOR ARC WORKING WITH GA SHIELDS HAVINGCOHERENT-STREAMING Filed April 25, 1960 9 Sheets-Sheet 9 6 2 6 n0 4 0 QI v 6 6 five L z 8 i I I I/ /.%l l, //l Q\ r/.. 1 I i. I M I f 0 i 7 m 41 5 P wvnvrms EUGENE F. GORMAN United States Patent 3,il53,9ti$ METHODAND APPARATUS FOR ARC WORKING WITH GAS SHKELDS HAVING CQHERENT-STREAMING Eugene F. German, Rutherford, and Robert J. Nelson,

Elizabeth, NJ., assignors to Union Carbide Corporation, a corporation ofNew York Filed Apr. 25, 1960, Ser. No. 24,550 34 Claims. (Cl. 219-74)This invention relates to are working, and more particularly to electricarc welding in a stream of shielding gas that protects the operationfrom natural air of the atmosphere.

Heretofore, the standard recommendation for obtaining optimum weldshielding has been to employ long nozzles or gas conduits having highL/De ratios. The impractically of such recommendation is evident when itis observed that commercial torches seldom provide any significantlength for gas passage. Welding trials have led us to the observationthat improved weld shielding can be obtained from a gas stream whichremains coherent for long distances after leaving the torch nozzle. Withthis point in mind, we determined the basic factors which influence theflow patterns of gases exiting from conduits.

We have observed that gross variations in weld shielding areencountered, depending on the method used to supply gas to nozzles. Theproblem of entering gas distribution has been investigated, but themethods developed, involved the use of large bulky chambers sometimeswith battles to gradually reduce turbulence in gas prior to its entryinto a downstream conduit or nozzle as shown in Mikhalapov Patent No.2,544,711.

In some cases, a plate with widely spaced drilled holes has beenproposed, but without much benefit. Prior to the present invention,therefore, it has been necessary to use torches with very long conduitsin order to obtain desirable shielding performance, which isinconvenient due to excessive length, bulk, and Weight. Present demand,however, is strongly in favor of torches of very short lengths, smallbulk, and light weight to permit maximum accessibility to confined workspaces, particularly for manual welding. As a result, welding operatorsprior to our invention had to pay critical attention to keeping thetorch nozzle very close to the weld in order to obtain acceptableshielding.

The main object of this invention is to provide novel means and methodsfor more effectively shielding with as little gas and as short a cup(nozzle) as possible in electric are working, such as arc weldingoperations, to improve the latter.

Another object of the invention is to provide a method of and means forprojecting a gaseous atmosphere of controlled purity and/ or compositionthrough a predetermined relatively long distance in the form of acoherent or solid" gas stream in the sense that the stream retains adesired form, purity, and composition without mixing with the ambient ofcontiguous atmosphere other than by non-turbulent aspiration.

Such method is used for the purpose of establishing a controlledatmosphere throughout a zone remotely located with respect to adischarge point. The controlled flow-pattern of the gas stream ischaracterized by a smooth and continuous, though not necessarilyuniform, distribution ofvelocities as represented by vectors which showboth the magnitudes and the directions of gas velocities throughout thestream cross-sections when a macroscopic rather than a microscopic scaleis used. This characteristic distribution of gas velocities isapplicable throughout all points in the stream cross-section starting atleast at that section where the stream exits from the projecting de-"ice vice and including all subsequent stream cross-sections up to andincluding a distance of at least 1 inch from the end of the projectingdevice. Such qualifying conditions, however, are specified for a testcondition wherein the stream is projected into free space and away fromany physical obstruction which would distort the test flow pattern ofthe gas stream. When these conditions are met in the test run, thedevice is then qualified to provide an extremely high degree ofatmosphere control over any zone which falls within the boundaries ofthe gas stream and up to a distance of at least 1 inch from the point ofdischarge thereof.

We have found that:

(1) The most important factor which must be con sidered in the design ofrelatively short gas conduits or nozzles for use in projectingcoherent-streams of gas is the state of velocity of the gas entering thenozzle.

(2) Very short nozzles can be used when gas enters in a favorable state.Conversely, the use of long nozzles is required only when gas enters inan unfavorable state.

(3) A favorable state exists when gas enters a nozzle or downstreamconduit at a velocity no more than about 5 times the required conduitvelocity and preferably less than 3 times the conduit velocity.

(4) Permeable barriers are the most efiective devices for producingfavorable states of entering gas flow.

(5) It is now possible by virtue of the invention to use specialpermeable barriers or gas lenses instead of nozzles to project coherentstreams of gas through very long distances before turbulent break-up ofthe gas stream occurs.

(6) With shaped gas lenses, phenomenally large areas of complete weldshielding can be obtained along with unrestricted visibility of thewelding operation and flexibility in the manipulation of a torch orshielding device.

(7) With the aid of gas lenses, it is now possible to eifect completecontrol over the magnitudes, directions, and distributions of velocitiesthrough gas streams so as to produce coherent-streaming independent ofReynolds numbers or L/De ratios.

In the drawings:

FIG. 1a is a fragmentary cross-sectional view of an arc Welding torchillustrating the invention;

FIG. lb is a similar view of a torch (Linde HW-l3) of the prior art;

FIG. 2a is a perspective view of a streaming pattern of gas leaving theprior art torch of FIG. 1b;

FIG. 2b is a similar view of a streaming pattern of gas leaving thetorch of FIG. 1a of the invention;

FIG. 3 is a graph of coherent-streaming distance-argon flow ratecharacteristic curves comparing the invention with the prior art;

FIG. 4a is a plan view (photograph) of aninert-gasshielded-non-consumable electrode weld made with the prior arttorch of FIG. 1b;

FIGS. 4b, 4c, 4d and 4e are similar views of welds made with torchescomprising the invention;

FIG. 5a is a view similar to FIG. 4b showing the weld shield span;

FIG. 5b is a graph of weld shielding span-nozzle-towork elevationcharacteristic curves comparing the invention with the prior art;

FIG. 6a is a view partly in cross-section and partly in side elevationshowing a gas lens positioned in the end of a gas supply conduit foraxial stream directional control;

FIG. 6b is a similar view of a gas lens positioned in the end of a gassupply conduit for axial and radial directional control;

FIG. 6c is a similar view of a diverging stream obtained with a convexgas lens (permeable barrier);

FIG. 7a is a cross-section of a nozzle provided with a gas lens for fiatprofile gas velocity control and which also produces an axially directedstream;

FIG. 7b is a similar view of a nozzle provided with a gas lens forparabolic profile gas velocity control, and which also produces anaxially directed stream;

FIG. 70 is a similar view of a nozzle provided with a gas lens forparabolic profile gas velocity control and which also produces adiverging stream;

FIG. 8a is a fragmentary view mainly in cross-section of a torchprovided with a flat gas lens;

FIG. 8b is a similar view of a torch provided with a parabolic gas lens;

FIG. 9 is a fragmentary view mainly in side elevation of a gas streampattern from a parabolic gas lens;

FIG. 10a is a plan view (photograph) of a prior art weld;

FIG. 10b is a similar view of a weld made with a torch provided with aflat gas lens;

FIG. 100 is a similar view of a weld made with a torch provided with aparabolic gas lens; and

FIG. 11 is a fragmentary view partly in cross-section of a torchillustrating the invention.

In prior standand inert gas shielded arc welding torches, gas issupplied to the downstream conduit or nozzle through one or more gasports. Such ports invariably have a total cross-sectional areaconsiderably less than that of either the nozzle or the immediatedownstream conduit. Laboratory experiments, however, have shown that adownstream conduit can exert a significant influence on the gas suppliedto it only when it is filled with the moving gas stream. If the area ofthe gas ports is less than that of the downstream conduit, then theconduit will not be adequately filled with the moving gas stream for anappreciable distance beyond the gas ports.

Contrary to prior knowledge, we have found that for all practicalpurposes, gas exits from the gas ports at atmospheric pressure. Fromthat point on, therefore, flow calculations should be made on the basisof incompressible, i.e., fully expanded, flow. For example, a staticpressure of only 0.18 p.s.i. will produce a velocity of 125 ft. persecond with argon, or 396 ft. per second with helium, for the case ofisentropic flow through a nozzle. Starting at such a low pressure, thegas can expand by an amount equal to only 1.2 percent of its originalvolume. Thus, it can be seen that gas from a small area stream will notexpand to fill a large area conduit. Instead, the gas velocity must bereduced by an appropriate amount to allow the gas to spread out. Theobservations to date, however, are that a moving gas stream has verylittle tendency to slow down, even when it meets a physical obstructionsuch as a conduit wall or bafile.

As shown in FIG. 1b, the HW-lS Linde torch 10 (made and sold by UnionCarbide Corporation), is typical of most prior standardtungsten-inert-gas shielded arc Welding torches in that the gas portsconsist of four holes 12 of /33 inch diameter which are drilled in acollet body 14. The illustrated torch is provided with a No. 10 /8 inchinside diameter) nozzle 16 and a inch diameter tungsten electrode 18.The total cross-sectional area of the gas ports 12 is 0.028 sq. in. At aflow (Q) of c.f.h., N.T.P. (normal conditions of temperature andpressure68 deg. F., 14.7 p.s.i.a.), the average velocity (V) of gasexiting from the gas ports is:

Q 1O cu. ft./hr. 1 hour A- 0.028 sq. in 3600 see.

14 1 sq. in. 10 X 1 sq. ft. 0.02s

4X 10* ft./see.

V: 14.2 ft./sec.

However, the cross-sectional area of the downstream conduit 20 at apoint just below the collet body 14 is 0509 sq. in. At incompressibleflow the average gas velocity at this downstream point for such areashould be no more than 0.78 ft./sec. when the conduit is running full at10 c.f.h. Thus, such use of such small gas port area causes the gas toenter the conduit 20 at a velocity Which is 18.2 times higher than thatrequired by the downstream area.

Studies by us of gas flow patterns inside and outside of conduits haveshown that the general mechanism, and perhaps the only one, by which asmall-area high-velocity stream is converted into a large-arealow-velocity stream is by turbulent transition. The high kinetic energyof the small stream, /2MV,, must be reduced to the lower value of thelarge stream, .MV The difference between these two terms representsexcess kinetic energy, /2M(V,, V which must be dissipated in some way.

Take as an example the above cited case wherein argon gas is fed throughportholes 12 at an average velocity of 14.2 ft. per second into a nozzle16 requiring an entering velocity of only 0.78 ft. per second. Theexcess kinetic energy per cu. ft. of argon is:

(0.78 ft./sec.) ]=0.32 ft. lb.

This amounts to (18.2) :33O times the kinetic energy between 1 and 8inches of conduit length is required merely for dissipation of suchsurplus energy, even when a baffle is employed.

From these observations we deduce that coherentstreaming cannot beproduced by a conduit until most of the excessive kinetic energy hasbeen eliminated and the conduit becomes filled with the moving gasstream. When such preliminary conditions are obtained at or near theprint of entry into the gas conduit, there exists a state of gas flowwhich is favorable to the development of a coherent stream. The lengthof nozzle required to produce coherent-streaming is largely determinedby the amount of excess kinetic energy which must be dissipated.

A series of modifications was made in which additional gas ports of thesame diameter were drilled in the collet body in order to reduce theentering gas velocity. Another approach was to insert a gas-permeablebarrier (porous plastic) 22, FIG. 1a, in torch 24 in a gas-tight sealingmount comprising a ceramic collar 25 and rubber gaskets 26 and 17disposed at the ends thereof. For this latter modification, the point ofgas entry into the nozzle 16 is the downstream face of the permeablebarrier 22.

Gas stream flow patterns obtained with the so modified torches werecompared with that of the prior standard torch. The flow patterns weremade visible by first adding oil vapor to the gas and by passing theexiting gas stream through a strong beam of light, which is a greatimprovement over use of the results obtained with Schlierin apparatus.For each torch system, measurements were made of the coherent-streamingdistance; that is, the distance through which the gas could be projectedas a solid stream into space without mixing with 5 TABLE 1 EfiectReduced Gas Velocity Upon Entering a Nozzle 1 Based on a conduitcross-sectional area of 0.509 sq. in. at a point just below the colletbody.

2 Obtained with 20 c.f.h. argon through a N o. 10 nozzle.

3 Assuming that the unobstructed downstream face area of barrier (0.444sq. in.) to contain 35% open area.

It can be seen from Table 1 that with each reduction in entering gasvelocity, the coherent-streaming distance is signifcantly increased.Whereas the standard 4-hole construction (18.2 area or velocity ratio)yielded a coherent-streaming distance of only /2 inch, the 16-holeconstruction (4.5 ratio) produced a distance of 21 inch, one and a halftimes that of the standard prior torch. With the permeable barrier (3.2ratio), a distance of 3 inches was obtained, six times that of thestandard torch. From the trend shown in such table, it appears thatsignificant increases in the coherent-streaming are obtained when theentering gas-velocity ratio was reduced to 5 or less. The increases werephenomenal, however, when the permeable barrier was used. It wouldappear then that in addition to providing the reduced entering velocityinto the nozzle, the permeable barrier also exerted some additionalcontrol over the gas to promote coherent-streaming.

FIGS. 2a and 2b are line drawings based on actual photographs of typicalold and new gas flow patterns at approximately full scale. Note that thecoherentstreaming flow pattern 26 of gas leaving torch 24, FIG. 2b, isconsiderably longer than that 29 leaving torch 10, FIG. 211.

Additional measurements of the coherent-streaming distance for variousstandard and modified torch systems were made with argon flows rangingfrom to 60 c.f.h. The results of such tests are shown in thecharacteristic curves of FIG. 3. From such curves, it is evident thatthe superior systems remain so throughout the full range of flows,although the coherent-streaming distances for all systems become lessfor increased flow rates. Similar improvements in coherent-streamingoccurs when gases other than argon are employed, such as He, N 0 and COThus, the techniques for producing extended coherent-streaming areapplicable to any gas. Because of the greater convenience in makingtests, the torches and hence the gas streamers were placed in thehorizontal position. The drooping which occurs at the low flow end ofthe permeable barrier curve is caused by gravity and slight draftsacting on the greatly extended coherentstream at low velocity. Ingeneral, flow rates adequate to produce gas velocities greater than 1ft./sec. are required to get suificient stifiness in the gas stream toovercome gravity and draft effects for streaming distances greater than1 inch.

Non-consumable electrodes, inert-gas shielded arc welding tests weremade with the various torch systems. Bead-on-plate welds were made oninch thick cold rolled steel at 150 amperes DCSP, 10 volts, i.m.p., andwith a flow of 25 c.f.h. of argon. FIGS. 4a, 4b and 4c are photographsat approximately 2 magnification of two sets of welds. The first set ofwelds, FIGS. 4a-4c, was made with the torch nozzle elevated inch abovethe surface of the weldment. The second set, FIGS. 4d and 42, was madewith the torch nozzle elevated 78 inch above the work surface. Thedegree of 6 weld shielding obtained in each case can be ascertained bythe extent of bright, undiscolored surface at the end of the weld. Atsuch point, the torch was stopped and weld current shut off, but argonflow was maintained as the welds were allowed to cool.

It can be seen that at a nozzle-to-work distance of inch, the priorstandard torch yielded very little weld protection, FIG. 4a. In thiscase the shielding was dependent almost entirely on the gas pumpingaction of the arc. When the nozzle was elevated an additional /8 inch,air was in contact with the electrode tip and are pumped into the weldto produce rough surfaced, badly contaminated welds. The l6-hole systemproduced good shielding at inch elevation, FIG. 417, while the torchwith the permeable barrier yielded excellent protection over a broadarea which includes the weld puddle and a large portion of the heataffected zone, FIG. 40.

When the nozzle elevation was increased to 78 inch, the 16-hole systemwas beyond its limit, FIG. 4d, whereas the permeable barrier continuedto produce good shielding, FIG. 40. This latter system producedexcellent shielding at distances in excess of 1% inch, but arc stabilitybecame a problem due to excessive extension of the electrode. Thisdifficulty can be eliminated by extending the collet body to provideelectrode cooling closer to the arc end of the electrode.

(FIG. 5a shows the weld shielding span distance S, and FIG. 5b shows agraph of the weld shielding span versus nozzle-to-work elevationobtained under these test conditions. It can be seen that the reductionof gas velocities upon entering a short nozzle leads to two importantprocess improvements:

(1) Greatly increased nozzle-to-work elevation at which good weldshielding can be obtained.

(2) Significantly increased weld shielding span for all nozzle-to-workelevations.

One important by-product of the use of enlarged gas port areas is theelimination of the jetting problem. In standard HW-13 torches, anannular clearance hole of 0.130 inch diameter is provided in the colletbody through which all electrodes of /s inch and smaller diameters areinserted. With inch or smaller diameter electrodes, gas jets at highvelocity through the annular clearance, resulting in serious impairmentand frequently the complete destruction of weld shielding. During ourtests we found that the use of the l6-hole system unexpectedlyeliminated the jetting problem, regardless of the size of the electrodeemployed. The increased area of the gas ports provided a path of leastresistance, such that little or no gas emerged through the clearancehole.

In contrast, when permeable barriers were placed in the torch, the gaspath through the barrier was generally one of relatively highresistance. As a consequence, the problem of gas jetting increased.Also, jetting could occur at any point where the gas leaked past thebarrier. We found that to successfully employ permeable barriers, it isnecessary to mount them in a leak-tight seal, FIG. la, to reduceelectrode clearance and to ensure that there are no cracks or relativelylarge voids in the barrier material through which jetting might occur.In Sigma welding with the permeable barrier mounted in HW-l3 torch, itwas also necessary to prevent gas jetting through the wire contact tip.This was accomplished by inserting the wire liner into a seat in theguide tube tip to act as a gas seal. In retrospect, perhaps one of themain reasons why earlier tests with permeable barriers were notparticularly successful was that the jetting problem was not recognized.

A wide variety of tests was made by us during which the patterns ofgases exiting from the surfaces of permeable barriers were examined.These tests were originally made to determine the degree to which theturbulence in a gas stream could be reduced prior to discharging the gasinto a nozzle. Included in these tests were filter materials of highdensity and ultra-fine porosity such that they normally would not beconsidered for use in an arc welding torch as they were considered to beinsufficiently permeable and too restrictive to the flow of gas. Thesematerials were carefully mounted in a test device in a tight sealingarrangement in order to evaluate the materials performance withoutinterference on account of jetting. Unexpectedly, we found that it waspossible to obtain a degree of gas flow control far beyond the meremoderation of turbulence. It was also possible to effect completecontrol over the flow pattern of gas exiting from a special class ofpermeable barrier, regardless of the de gree of turbulence in the gas assupplied to the barrier. Coherent-streaming through very long distancescould be obtained with the permeable barrier alone, thus eliminating theneed for any downstream conduit.

We also found that if the permeable barrier were properly constructed,then gas exited from the barrier in a direction which is perpendicularto the barriers local surface. This phenomenon is independent of thedirection or condition at which the gas flowed into the barrier. FIGS.60, 6b, and 6c show means for controlling the directions of gas streamswith various shapes of permeable barriers. FIGS. 6a and 6b show gasstreams 30 and 32-34 obtained with a cylindrical plug or lens 36 made ofdensely packed felt fiber. When mounted flush with the end of the gassupply conduit 31, an axial stream is obtained. When the plug ispartially extended, both axial and radial gas streams 32 and 34,respectively, are simultaneously obtained. Finally, as shown in FIG. 60,a convex barrier or lens 38 made of felt produces a diverging stream 40.Surprisingly, this latter stream remains coherent for an appreciabledistance beyond the external (discharge) surface of the barrier or lens.

The degree of directional control which a permeable barrier imposes onthe gas is primarily related to the fineness of the voids rather thanthe thickness of the barrier. For example, it is possible to use asingle layer of fine mesh wire filter cloth instead of a relativelythick section of densely packed fibers, or porous media made of metalceramics or fritted glass. Thus far, tests have revealed such a trend. A60-mesh copper wire cloth (0.010 in. square opening, 0.0075 in. diameterwire) exerted a slight direction control. A ZOO-mesh copper wire cloth(0.03 in. square opening, 0.002 in. diameter wire) exhibited a highdegree of directional control. In general, the smaller the size ofopening, the greater will be the directional control over the gasflowing through the permeable barrier. The flow control effects of suchpermeable barriers are additive in that multiple layers can beassembled, preferably spaced a short distance apart from each other,with the result that a greater degree of directional control can beobtained.

Thus, wire cloths with larger openings can be used if they are stackedin multiple layers. For example, three layers of 60-mesh wire clothspaced /8 in. apart yield results which are equivalent to a single layerof ZOO-mesh wire cloth. In the case of porous metal compacts, fiberouspackings, etc., when thicknesses of in. and /s in. are used, the testsshowed that mean pore dimensions of the order of 0.004 in. or less arestill required for good results. The Kel-F plastic material used for thewelding tests shown in Table 1 was in. thick with a mean pore diameterof 0.005 in.

A comparison between the performance obtained with fine mesh wire filtercloth, densely packed fibers, and sintered metal porous compacts gavefurther insight into the basic requirements for the control ofcoherent-streaming. We observed that the cloths yielded a uniformdistribution in both the magnitude and direction of the gas velocityprimarily because of their uniform pore size and close spacing of thepores. The fiber and porous metal barriers, however, often produced anirregular distribution in velocities unless particular care was takenduring construction to insure a controlled distribution of gaspermeability. At some points in these barriers, the packing was tootight in relation to other points where the pack ing was too loose. Theresult was an irregular distribution of zones of low, medium, and highvelocity flow which interfered with coherent-streaming. In some cases,the high velocity portions constituted jetting which disrupted the flowcharacteristics of the remaining portions of the gas stream. In othercases, there was such a great difference in the velocities as to resultin a cluster of separate streams spaced from each other in a mannerroughly analogous to the flow of water from a shower head or a gardensprinkler. Air penetrated between the separated streams to cause weldcontamination.

In contrast, with a permeable barrier constructed to produce a smoothand continuous distribution of gas velocities, excellentcoherent-streaming and hence, weld shielding, was obtained.

FIGS. 7a, 7b and 7c illustrate ways of controlling the distribution ofgas velocities by varying the thickness and hence the gas permeabilityof the lenses. As shown in FIG. 7, a flat disk-shaped lens 42. in theoutlet of a cylindrical gas chamber 44 produces a coherent-stream 46 ofgas having essentially constant velocity throughout the cross-sectionalarea, as indicated by vectors 47. In FIG. 7b, lens 43 having a flatdownstream face and a concave upstream face 49, produces acoherent-stream 50 having a parabolic distribution of velocities 51.Concave-convex lens 52, FIG. 70, produces a divergent coherentstream 53having a parabolic distribution of velocities 54. Streams with aparabolic velocity profile are more stable, and produce longercoherent-streaming distances than streams with a fiat velocity profile.Such streams will often be preferred to insure maximum control ofatmospheric composition, particularly at points Where the streamimpinges on a solid surface.

When gas lenses are employed, coherent-streams can be producedregardless of the Reynolds numbers of L/De value which have frequentlybeen used in the past as mathematical specifications for flowconditions. Our findings are that such numbers do not insure laminar ornonturbulent flow, but rather they indicate a possibility for laminarflow. In laboratory tests, it was possible to obtain coherent-streamingdistances of 3 to 6 inches under conditions which would correspond toReynolds numbers of the order of 5000 and L/De ratios equal to zero. Atthe present time, there are strong indications that coherent-streamingthrough appreciable distances can be obtained at Reynolds numbers atleast up to 15,000 with the aid of gas lenses.

It 'must be noted, however, that the calculation of Reynolds numbersapplies only to a gas stream cross-section within conduit walls. Hence,when permeable barriers or gas lenses are used without a downstreamconduit, e.g., L/DQEO, then Reynolds numbers do not apply.

From these tests it is apparent that the use of a special class ofpermeable barriers results in a degree of control over gas flow patternsfar beyond that which could be obtained with conduits or nozzles. Thisspecial class consists of devices made from permeable materials whichproduce a relatively smooth and continuous distribution of gasvelocities, in terms of both magnitude and direction, across thedownstream surface of the permeable material even when gas is suppliedto the barrier in a state of gross turbulence. Since these permeablebarriers act on gas in much the same manner as a glass lens acts inshaping a beam of light, the analogous term gas lens has been applied tothem by us.

FIG. 8a shows an arc torch comprising flat gas lens 56, and FIG. 8bshows an arc torch comprising a parabolic lens 58, each being ofconstant thickness. Gas streaming and weld shielding made with the flatlens 56 alone yield results that are comparable to those previously obtained when the lenses were mounted inside and upstream of the nozzle16, FIG. 1a.

FIG. 9 is based upon a photograph of a diverging gas stream 59 obtainedwith the parabolic lens 58.

Such lens yields a phenomenal increase in the surface area of protectionon body B.

FIGS. 10a, 10b, and 10c are photographs of welds made with three basicsystems: (1) standard HW-13 and No. 10 nozzle, (2) modified HW-13 torchand No. 10 nozzle with flat gas lens, and (3) modified HW-13 torch withparabolic gas lens. Bead-on-plate welds were made on A inch thick coldrolled steel with argon flow of 60 c.f.h. The welding conditions were 15i.p.m., 130 amperes DCSP, and 10 volts. Very short nozzle-to-Workdistances were employed in order to obtain good weld shielding, FIG.10a, even with the standard torch. The noZzle-to-Work distance for thefirst two torch systems Was inch. The vertex of the parabolic gas lenswas positioned at /2 inch above the work. It can be seen from thesepictures that all systems yielded good shielding at such shortelevations and at the high gas flow rate used. There is, however, asubstantial difference in the extent of weld protection obtained withthe different systems. The use of a nozzle with a fiat gas lens produceda broader coverage, FIG. 10b, than that obtained with the prior standardnozzle alone. The parabolic gas lens, however, produces a substantiallybroader coverage, FIG. 10c, than everobtained with any prior system ofcomparable size.

The maximum area of perfect shielding which can be obtained with asimple nozzle under the best conditions is only slightly larger than thearea of the nozzle. The parabolic lens, however, was 1% inch in diameterat the torch junction, yet it produced an area of perfect shielding or"3 inches diameter. Thus, the area of perfect shielding obtained with theparabolic lens is approximately 8 times the lens area. The performanceis similar to that of a leading-trailing shield, but with none of theusual restrictions on are visibility, torch manipulation oraccessibility to the weld joint. Such parabolic lens is, thus, of greatvalue for the gas shielded arc welding of reactive metals such astitanium, molybdenum, etc.

The significance of such results is that entirely new shielding devicesare now possible. Such devices produce both maximum quality of weldshielding and maximum flexibility of operator usage. They can betailored to any system where a controlled streaming pattern of gas orgases is desired. For welding, the lens can be used with or in place ofprior standard or multi-wall torch nozzles. They may also be used asauxiliary gas shielding devices with the same or different gases as areused in the torch.

As a result of the foregoing, we have discovered that:

(1) In the standard HW-13 torch, gas enters the nozzle at velocitiesapproximately 18 times greater than the required nozzle velocity for agiven flow rate.

(2) With the standard HW-13 torch, good weld shielding is obtained onlywhen the nozzle-to-work distance is /2 inch or less.

(3) Various methods for reducing the velocity of gas entering a nozzlecan be successfully employed including the use of additional gas portsin the torch collet body and the use of a permeable barrier mountedinside the torch nozzle.

(4) Good weld shielding at nozzle-to-Work distances of up to 4 inch orless was obtained when the entering gas-velocity ratio was reduced to4.5.

(5) Good weld shielding at nozzle-to-work distances of over 1% inches isobtained when the entering gasvelocity ratio is reduced to 3.2.

(6) Excellent weld shielding is also obtained when a permeable barrieris used alone as a nozzle.

(7) Permeable barriers when properly constructed as gas lenses can beused to control the magnitude, direction and distribution of gasvelocities in the exiting gas stream.

(8) Complete control of gas flow patterns can be ob tained withpermeable barriers or gas lenses made of densely packed fibers, finemesh wire filter cloths or- 10 such materials Were of the order of 0.010inch or less.

(9) Coherent-streaming distances of the order of 3 to 6 inches can beobtained by the invention at flow conditions equivalent to Reynoldsnumbers of over 5000 and L/De ratios down to zero.

(10) Parabolic-shaped gas lens attached to an HW-13 torch produces abroad area of perfect shielding equal to eight times the lens area.

(11) With the parabolic lens used in place of or as a nozzle, there isessentially no interference with are visibility and joint accessibilityin contrast to that which must be tolerated when prior nozzles are used.

According to the invention apparatus for producing a favorable state ofentering gas flow into a relatively short nozzle comprises barrierswhich have a multiplicity of very small pores, such pores having meanpore diameters of 0.020 inch or less as determined on the basis of thefollowing calculation:

where Azaverage plane area of pores, inches. P=average perimeter ofpores, inches.

Such barriers can be made of any suitable material having a multiplicityof very small (tiny) openings, holes, pores, or interstices eitherrandomly or uniformly spaced. The openings may be interconnected as infiber or granular compacts or they may be not interconnected as in athin plate with a multiplicity of drilled holes.

The permeable barriers also can be made from fibers, powders, granules,beads of material prefer-ably able to withstand temperatures of 300degrees F. or more, either metallic or nonmetallic, or from solids whichhave been perforated mechanically as by drilling or punching, or bychemical means as by etching.

Also contemplated by the invention are:

Permeable barriers in the form of a wall, layer, or membrane of eitherconstant or smoothly varying thicknesls1 not to exceed inch andpreferably less than inc Permeable barriers comprising one or moreseparate walls, layers or membranes and preferably spaced apart fromeach other a short distance of the order of at least five mean porediameters of 0.020 inch;

Permeable barriers wherein the total equivalent crosssectional area ofsaid pores is equal to or greater than 20 percent of the totalcross-sectional area of the permeable barriers;

Permeable barriers wherein the pores are closely spaced with respect toneighboring pores with an average centerline spacing of not more than 10mean pore diameters or 0.040 inch maximum according to whichever is thesmgller dimension with respect to the given pore size; an

Permeable barriers (gas lenses) having mean pore diameters of 0.010 inchor less.

As shown in the drawing, FIG. -1 1, gas lens 60 is attached to a holder(preferably non-permeable) 62 which is threaded onto the torch colletbody 64 until tight contact is made with the gas seals 66, 68 to preventjetting. Also, individual close fitting electrode collets 70 areprovided for each size of electrode '72 to prevent jetting through thecollet body-electrode clearance hole 74. Such lens embodies many of thebest features of the invention and has curved surfaces 76 to provide acomposite gas stream simultaneously having divergent, constant area andconverging flow characteristics. The diverging portion of the streamprovides maximum area of Work surface shielding from a minimum size ofgas lens. The constant area and converging portions of the gas streamprovide maximum coherent-streaming distances. Also shown in dottedoutline for comparison on FIG.

11 are two relatively small standard nozzles (Linde) N0..

8 6 inch LD.) and No. inch I.D.). Such nozzles would provideconsiderably smaller zones of workpiece shielding about the arc and mustbe used at relatively short nozzle-to-work distances. Despite the factthat they are relatively small nozzles, they still have considerablebulk which, in combination with their limited shielding performance,imposes interference with arc visibility and torch maneuverability,particularly when welding in confined spaces. In contrast, the gas lens60 of the invention has substantially less bulk, and since it providesbroad area shielding and permits welding at relatively long lens-to-workdistances, it eliminates such prior standard nozzle limitations.

The invention is not restricted to electric arc welding with anon-consumable or refractory electrode, but is equally applicable tosigma welding in which a consum able wire electrode is used, as well asother kinds of operations in which gas protection from the atmosphere isinvolved.

What is claimed is:

1. Process in which work is shielded from ambient air with a stream ofgas flowing in the form of a beam, which comprises dividing a flowcomposed of such gas into a multiplicity of separate paths, the gas ofwhich upon discharge merges substantially without turbulence, fullyexpanded, to create such beam, such paths being characterized by verysmall cross sectional areas and close spacing with respect toneighboring paths, resulting in coherent streaming of such gas thelength of such beam prior to discharge into space being less than 3inches by virtue of the merger substantially without turbulence of suchseparate paths in the creation of such beam, and applying the sodischarged beam of gas against the surface of said work, to therebyobtain maximum eflective shielding of such work with such gas.

2. Process of are working with an electrode, the arcend of which isshielded with a stream of gas flowing in the form of a columnsurrounding such electrode, which comprises dividing such stream into amultiplicity of separate paths, the gas flowing through which upondischarge merges without turbulence, fully expanded, to create suchcolumn, such paths being characterized by small cross sectional areasand close spacing with respect to neighboring paths, said separate pathsresulting in coherent-streaming of such gas in free space around the endof such electrode, the length of such column prior to the discharge intofree space being less than 20 times the equivalent diameter of suchcolumn by virtue of the merger without turbulence of such separate pathsin the creation of such column.

3. Process of welding with an elongated consumable wire electrode, thearc-end of which is shielded with a stream of gas flowing in the form ofa column surrounding such electrode, which comprises dividing suchstream into a multiplicity of separate paths the gas through which upondischarge merges without turbulence, fully expanded, to create suchcolumn, said paths being characterized by small cross sectional area andclose spacing with respect to neighboring paths, resulting incoherent-streaming of such gas in free space around the end of suchelectrode, the length of such column prior to discharge into free spacebeing less than 5 times the equivalent diameter of such column by virtueof the merger without turbulence of such separate paths in the creationof such column.

4. Gas stream-shielded are working in which the arc is energized betweenan electrode and a workpiece, which comprises shielding the end of suchelectrode and the arc and the adjacent metal being welded with a streamof arc shielding gas flowing in a direction parallel to the longitudinalaxis of such electrode, characterized in that such stream is dividedinto a multiplicity of separate paths immediately (less than 3 inches)prior to the discharge thereof into free space around such electrode tothereby provide coherent-streaming of the so-discharged fully expandedgas in a direction that is controlled for a subi2 stantial distancetherefrom, effectively shielding the operation from the air.

5. Gas stream shielded are working in which the arc is energized betweenan electrode and a workpiece, which comprises shielding the end of suchelectrode and the arc and the adjacent metal being welded with adiverging stream of arc shielding gas, characterized in that such streamis divided into a multiplicity of separate paths immediately (less than3 inches) prior to the discharge thereof into free space around suchelectrode to thereby provide coherent-streaming of the so-discharged,fully expanded gas effectively shielding the operation from air.

6. Gas stream shielded are working in which the arc is energized betweenan electrode and a workpiece, which comprises shielding the end of suchelectrode and the arc and the adjacent metal being welded with aconverging stream of arc shielding gas, characterized in that suchstream is divided into a multiplicity of separate paths immediately(less than 3 inches) prior to the discharge thereof into free spacearound such electrode to thereby provide coherent-streaming of theso-discharged fully expanded gas, effectively shielding the operationfrom air.

7. Gas stream shielded are working in which the arc is energized betweenan electrode and a workpiece, which comprises shielding the end of suchelectrode and the arc and the adjacent metal being welded with acomposite stream of arc shielding gas, which simultaneously includesdivergent, constant area and convergent flow characteristics in suchcomposite stream characterized in that such stream is divided into amultiplicity of separate paths immediately (less than 3 inches) prior tothe discharge thereof into free space around such electrode to therebyprovide coherent-streaming of the so-discharged fully expanded gas,effectively shielding the operation from air.

8. Gas stream shielded arc working in which the arc is energized betweenan electrode and a workpiece, which comprises shielding the end of suchelectrode and the arc and the adjacent metal being welded with a streamof arc shielding gas with a constant velocity throughout the streamcross section, characterized in that such stream is divided into amultiplicity of paths of equal gas permeability immediately (less than 3inches) prior to the discharge thereof into free space around suchelectrode to thereby provide coherent-streaming of the so-dischargedfully expanded gas in a direction that is controlled for a substantialdistance therefrom, effectively shielding the operation from air.

9. Gas stream shielded are working in which the arc is energized betweenan electrode and a workpiece, which comprises shielding the end of suchelectrode and the arc and the adjacent metal being welded with a streamof arc shielding gas with a parabolic distribution of gas velocity inthe stream cross section, characterized in that such stream is dividedinto a multiplicity of paths of suitably varying gas permeabilityimmediately (less than 3 inches) prior to discharge thereof into freespace around such electrode to thereby provide coherent-streaming of theso-discharged fully expanded gas in a direction that is controlled for asubstantial distance therefrom, effectively shielding the operation fromair.

10. Gas stream shielded are working in which the arc is energizedbetween an electrode and a workpiece, which comprises shielding the endof such electrode and the arc and the adjacent metal being welded with acomposite stream of arc shielding gas which simultaneously includesdivergent, constant area and convergent flow characteristics in suchcomposite stream, said composite stream having a constant velocitythroughout the stream cross section, characterized in that such streamis divided into a multiplicity of paths having equal gas permeabilityimmediately (less than 3 inches) prior to the discharge thereof intofree space around such electrode to thereby provide coherent-streamingof the so-discharged fully expanded gas, eflectively shielding theoperation from air.

11. Gas stream shielded are working in which the arc is energizedbetween an electrode and a workpiece, which comprises shielding the endof such electrode and the arc and the adjacent metal beirg welded with acomposite stream of arc shielding gas which simultaneously includesdivergent, constant area and convergent flow characteristics in suchcomposite stream, said composite stream having a parabolic distributionof gas velocity in the stream cross section, characterized in that suchstream is divided into a multiplicity of paths having. suitably varyinggas permeability immediately (less than 3 inches) prior to the dischargethereof into free space around such electrode to thereby providecoherent-streaming of the so-discharged fully expanded gas, effectivelyshielding the operation from air.

12. A gas-shielded arc torch comprising an elongated electrode, anelectrical contact for said electrode, means supporting said contact,said means having an annular chamber and are shielding gas passages fordelivering arc shielding gas to such chamber, and a gas lens surroundingsaid electrode and constituting a wall of such chamber, for fullyexpanding and directing such gas around said electrode in the directionof the arc end thereof.

13. A gas-shielded arc torch as defined by claim 12, in which said gaslens is shaped so that gas components are directed thereby to convergetoward said electrode flow parallel to the axis thereof, and divergeaway from said electrode.

14. A gas-shielded arc torch as defined by claim 12, provided with meansfor preventing jetting of such gas adjacent said electrode.

15. A gas-shielded arc torch comprising an electrical contact memberincluding a collet body provided with radial gas ports, an elongatedelectrode mounted in such collet body, and agas cup surrounding such gasports in spaced relation for receiving gas therefrom and dischargingsuch gas around the arc end portion of said electrode, characterized inthat said ports are sufiicient in size and number to substantiallyreduce resistance to the flow of such gas therethrough compared withflow through other paths including undesirable jetting paths adjacentsaid electrode, and deliver the gas to said cup in a favorable state,the combined area of said ports being equal at least to 20% of thenozzle total exit area whereby the velocity of the gas discharged fromsuch ports is effectively reduced to moderate turbulence.

16. A gas-shielded arc torch comprising an electrical contact memberincluding a collet body provided with radial gas ports, an elongatedelectrode mounted in such collet body, and a gas cup surrounding suchgas ports, in spaced relation for receiving gas therefrom anddischarging such gas around the arc end portion of said electrode,characterized in that a gas permeable barrier is mounted within said gascup around said electrode for transforming gas delivered thereto by suchports into a favorable state upon discharge therefrom, and means sealingthe spaces between said ports against gas leakage including undesirablegas jetting adjacent said electrode.

17. A gas-shielded arc torch comprising an electrical contact memberincluding a collet body provided with radial gas ports, an elongatedelectrode mounted in such collet body, and a gas cup surrounding suchgas ports in spaced relation for receiving gas therefrom and dischargingsuch gas around the arc end portion of said electrode, characterized inthat a gas lens is mounted in the outlet of said cup around saidelectrode, and means sealing the spaces between said ports against gasleakage including undesirable gas jetting adjacent said electrode.

18. Method of projecting a gaseous atmosphere of controlled purity andcomposition in ambient atmosphere through a predetermined distance inthe form of a coherent gas stream in the sense that such stream retainsa desired form, purity and composition without mixing with the ambientatmosphere other than by non-turbulent aspiration, for the purpose ofestablishing a controlled atmosphere throughout a zone remotely locatedwith respect to the point of discharge, the controlled flow-pattern ofsuch gas stream being characterized by a smooth and continuous, thoughnot necessarily uniform, distribution of velocities as represented byvectors which represent both the magnitudes and the directions of gasvelocities throughout the stream cross-sections when a macroscopicrather than a microscopic scale is used, such characteristicdistribution of gas velocities being applicable throughout all points inthe stream cross-section starting at least at that section where thestream exits from the projecting device and including all subsequentstream cross-sections up to and including a distance of at least 1 in.from such discharge point, wherein the stream is projected into freespace and away from any drafts and physical obstructions which woulddistort a test flow pattern of the gas stream, such qualifying testassuring the formation of an extremely high degree of atmosphere controlover any zone which falls Within the boundaries of the gas stream and upto a distance of at least 1 in. from such point of dis charge, whichmethod comprises dividing such gas, prior to discharge into free space,into a multiplicity of separate minute paths of close spacing withrespect to neighboring paths, the gas of which, upon discharge, mergeswithout turbulence, fully expanded, to create such streams, the meanpore diameter of said paths being less than 0.020 inch with a mean porespacing of 0.040 inch maximum. 19. Method employing relatively short gasconduits for projecting a gas stream therefrom into free space withcontrolled flow patterns in which gas is supplied to the conduit in afavorable state characterized by a velocity which is not more than livetimes greater than the downstream conduit velocity, and preferably lessthan three times the downstream conduit velocity, calculated on thebasis of imcompressible flow at 68 deg. F. and 14.7 p.s.i. abs. with theconduit running full so that there are no stagnant zones throughout thecross-section of the conduit, which comprises feeding such gas into arelatively short (less than 3 inches long) conduit through amultiplicity of separate paths the combined total effective area ofwhich produce in the gas discharged from such path such favorable statein such conduit, and maintaining effective successive, downstream,cross-sectional areas of gas within such conduit no greater than that ofthe upstream areas thereof.

20. Apparatus for producing a favorable state of entering gas flow in anozzle, comprising a permeable barrier wherein the total equivalentcross-sectional area of the pores in said permeable barrier is equal toor greater than 20 percent of the cross-sectional area of the permeablebarrier through which gas enters to be discharged therefrom at afavorable state with reference to the downstream side thereof in suchnozzle.

21. Apparatus for projecting coherent streams of gas from a relativelyshort conduit at Reynolds numbers Re= VDe) u up to 15,000 in which gasenters the conduit in a favorable state and at a velocity no more thanfive times the required downstream velocity, which comprises a gaspermeable barrier wherein the total equivalent crosssectional area ofthe pores in said permeable barrier is equal to or greater than 2-0percent of the cross-sectional area of the permeable barrier located insaid conduit.

22. Apparatus for producing favorable states of entering gas flow into arelatively short nozzle, comprisin a permeable barrier wherein the totalequivalent crosssectional area of the pores in said permeable barrier isequal to or greater than 20 percent of the total cross sectional area ofthe permeable barrier which has a multiplicity of very small pores, suchpores having mean pore MPD=4X 3 where A=average plane area of poresP=average perimeter of pores 23. Apparatus for projecting a coherentstream of gas comprising the combination of a gas supply system, agas-flow pattern forming nozzle connected to the extreme end of said gassupply system and a permeable barrier mounted in said nozzle, saidnozzle having a smooth internal wall surface, and an L/De ratio of from/2 to 20 with the cross-sectional area not increasing as the streamproceeds through and out of said nozzle.

24. Apparatus for projecting a coherent stream of gas comprising thecombination of a gas supply system, a gas-flow pattern forming conduitlocated at the extreme end of the gas supply system, a gas lensassociated with such conduit, said conduit having a smooth internal wallsurface with an L/De ratio of from to 20, said internal Wall surfacebeing non-divergent in the direction of flow of such gas stream.

25. Apparatus for projecting coherent streams of gas consisting of acombination of a gas supply system, a gasflow pattern forming nozzlewith a permeable barrier comprising a gas lens which is mounted in saidnozzle or at the extreme end of said gas supply system, the downstreamsurface of said gas lens having a convex face such that a diverging gasstream is discharged thereby.

26. Apparatus for projecting a coherent stream of gas consisting of acombination of a gas supply system, and a gas lens located at the outletend of such system which discharges a coherent stream of such gastherefrom, said gas lens having main pore diameters of 0.010 in. or lessand also having a total equivalent cross-sectional area of the poresequal to or greater than 20 percent of the total cross-sectional area ofthe gas lens.

27. Apparatus comprising a gas, lens for projecting a controlled flowpattern of gas characterized by a relatively smooth and continuous(though not necessarily uniform) distribution of velocity in terms ofmagnitude and direction across a downstream cross-section locatedapproximately A in. from the outside surface of said gas lens andthroughout all subsequent cross sections further downstream for adistance of at least 1 inch from said lens.

28. Shaped permeable barriers comprising a gas lens for projecting acoherent gas stream in a controlled flow pattern of gas therefromdepending upon the shape of said lens, said gas lens having minimum porediameters of 0.010 in. or less and also having a total equivalentcross-sectional area of the pores equal to or greater than 20 percent ofthe total cross-sectional area of the gas lens.

29. Apparatus comprising a gas chamber having a Wall provided with apermeable barrier composed of material containing a multiplicity ofholes having minimum pore diameters of less than 0.020 in. and saidholes occupying a total equivalent cross-sectional area equal to orgreater than 20 percent of the total cross-sectional area of thepermeable barrier so that such permeable barrier projects acoherent-stream of nitrogen gas of /2 in. diameter through quiescent airfor a distance of at least /2 in. at a flow rate of 15 c.f.h, nitrogen,and means for supplying gas to such chamber.

30. An arc torch comprising an electrode, a gas cup surrounding saidelectrode in spaced relation, means for supporting said cup andelectrode in spaced relation with each other, means for feeding gas tothe space between said cup and electrode, and a gas lens comprising agas permeable barrier mounted at the outlet of such space fordischarging such gas as a coherent stream therefrom to shield thearc-end of said electrode from the surrounding air.

31. The combination with an arc torch as defined by claim 30, ofelectric are power supply means connected to said electrode and to aworkpiece which also is shielded by such coherent gas stream in the areaof an arc energized between the end of said electrode and such workpieceby said electric are power supply means.

32. Apparatus for discharging a coherent stream of gas to shield fromthe air an arc energized between two electrodes which comprises a gaschamber surrounding one of said electrodes, and means for supplying gasthereto, the outlet of such chamber being provided with a gas permeablebarrier comprising a lens through which gas flows from such chamber,said lens acting to transform said flow into a coherent stream of gasaround such arc, the external flow pattern of such stream beingdetermined by the shape of said lens.

33. Apparatus as defined by claim 32, including means for feeding one ofsaid electrodes through said chamber and lens toward such are as suchelectrode is consumed thereby.

34. In a process for electric arc working materials wherein an arc isestablished between two electrodes and the arc effluent is appliedagainst the material to be worked and wherein both the arc efliuent andthe zone of the material being treated is shielded with a stream offlowing gas the improvement which comprises dividing said flowing gasstream into a multiplicity of separate paths, such paths beingcharacterized by having minimum pore diameters of 0.020 in. or less andclose spacing with respect to neighboring paths resulting in coherentstreaming of such gas, the length of such gas stream prior to dischargeinto space being less than 3 in. by virtue of the merger substantiallywithout turbulence of such separate paths in the creation of suchstream.

References Cited in the file of this patent UNITED STATES PATENTS1,669,362 Watson May 8, 1928 2,544,711 Mickhalapov Mar. 13, 19512,977,457 Houlderoft et al. Mar. 28, 1961 UNITED STATES PATENT OFFICECERTIFICATE OF CORRECTION Patent No. 3,053,968 September ll, 1962'Eugene F. Gorman et al,

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 1, linev59, for "of" read or column 2, line 39, for "through"read throughout column 4, line 58, for "17" read 27 column 5, line 56,for "streamers" read streams column 8, line 36 for "of", secrondoccurrence, read or Signed and sealed this 15th day of January 1963.

IEAL) testz' NEST w. SWIDER DAVID LADD iesting Officer Commissioner ofPatents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,053,968 September 11, 1962' Eugene F. Gorman et a1,

corrected below.

Column 1, line.59, for "of" read or column 2, line 39, for "through"read throughout column 4, line 58, for "17" read 27 column 5, line 56,for "streamers" read streams column 8, line 36,, for "of", seqondoccurrence, read or Signed and sealed this 15th day of January 1963.

#EAL) test:

NEST w. SWIDER DAVID LADD iesting Officer Commissioner of Patents

